During a sentence hearing on Friday, Judge Robert Newlinds questioned why Maaz, who had a successful history running a construction business, would pay far more for the machine than it was worth.

Maaz's barrister Greg Stanton told the court his client had been approached by another man, Raymond Lipovac, who he claimed was a business associate.

Maaz said during his trial that Lipovac told him whatever he spent above his $150,000 budget for a new excavator, would be reimbursed by another man in Queensland, who Maaz did not know.

Ultimately, Maaz purchased the machine for $288,000, well over the reserve price, explaining later that he had not made any inquiries into the value or history of the excavator before placing a bid.

During the auction, Maaz also on one occasion bid against himself, which Judge Stanton described as "to say the least, odd".

Australian Border Force became suspicious of an X-ray taken after the 42-tonne excavator arrived at Port of Brisbane from Southampton, in the UK, in March 2020.

Australian Federal Police officers examined it, finding and removing 226 bags containing a crystalline substance later identified as MDMA with an estimated wholesale value of more than $13 million.

Surveillance devices and a location tracker were fitted before the excavator was shipped to the Gold Coast, where it was listed for auction.

Maaz pointed to his successful construction business as evidence he had no reason to willingly take part in a major drug importation scheme. 

Judge Newlinds agreed Maaz's motive were unclear, given he did not seem to have a drug dependency, or any other reason to engage in such behaviour.

“I have no idea then why he did it other than some vague notion he was greedily trying to get some extra money,” Judge Newlinds said.

Maaz will be sentenced at a later date.